Igneous Rocks Inquiry Lab (In Person)

Revising authors: Mary Abercrombie, Florida Gulf Coast University (mabercrombie@fgcu.edu); Jennifer Cholnoky, Skidmore College (jcholnok@skidmore.edu)

Original authors: Mary Abercrombie, Florida Gulf Coast University; Lee Falkena, University of Illinois Chicago; Jessica Wolk-Stanley, Riverdale Kingsbridge Academy


Average inquiry level: Guided inquiry

This is an in-person inquiry lab for igneous rocks, but it could be converted to an online lab through use of igneous rock photos available online (see links provided in the Instructor Notes). Students will work with a variety of typical igneous rocks, developing observational skills and learning to categorize and identify igneous rocks based on their compositions and textures. In addition, students will be able to "tell the story" of igneous rocks, using observational skills to understand where on earth and under what circumstances an igneous rock could form.

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This lab is designed for a college undergraduate 100-level or introductory course for non-majors and/or majors. It would also be useful for a high school earth science course.

Skills and concepts that students must have mastered

For this lab, students are expected to have the following prior knowledge/skills:

  • Earth's formation/early earth conditions
  • Plate tectonic settings/processes
  • Making observations
  • Sketching (developing skill)
  • Mineral identification (developing skill)

How the activity is situated in the course

This activity would be situated early in a general or introductory earth sciences course. It could be a stand-alone exercise, although more typically, it would be the first in a series of inquiry-based rock labs that would also include sedimentary and metamorphic rocks.


Content/concepts goals for this activity

  • Creation of a detailed sketch of an igneous rock, including notes and observations.
  • Arranging igneous rocks into subcategories based on observations.
  • Defining and understanding terminology that geologists use to describe igneous rock textures and compositions.
  • Describing formation processes and environments (slow vs. fast cooling, mantle vs. continental melt, etc.) based on textures and composition.

Higher order thinking skills goals for this activity

  • Collaboration with peers to come to consensus on rock identifications;
  • Using observations along with a graphic scheme for igneous rock identification to identify samples of common igneous rocks.
  • Interpreting observations to develop descriptions of rock formation and plate tectonic settings
  • Developing explanations of rock "stories" that are supported by evidence/observations.

Other skills goals for this activity

  • Searching reputable sources for definitions of terms;
  • Presenting findings to a larger group;
  • Developing consensus on identifications based on observations.

Description and Teaching Materials

, Please see attached files for teaching materials: instructor notes, student packet, and instructor slides. The Instructor Notes include links to open access resources as well as online resources that can be used to transition this lab to an online format.

In addition, you will need the following:

  • Hand samples of the following, in trays or on index cards labelled by number or letter:
    • Granite
    • Diorite
    • Gabbro
    • Basalt
    • Rhyolite
    • Andesite
    • Pumice
    • Obsidian
    • Vesicular Basalt or Scoria
    • Pegmatite (optional)
    • Peridotite (optional)
  • A variety of large igneous rock samples to be used for the Mystery Rock activity: One for each lab group; Utilize the list above to pull appropriate samples.
  • Identification tools:Hand lens or magnifying glass
    Optional: cell phone app (search for "Cellular phone microscope" in Amazon)
  • Handouts (provided):
    • Student packet
  • Background readings (optional - resources provided below)
  • Communication Tools for sharing information/rock identifications (optional):
    • Group whiteboards & dry erase markers OR
    • Chalkboard & chalk OR
    • Large sheets of paper & markers

For all materials include, in the box below, a brief description of each item covering what it is and what its role is in the activity.

This activity asks students to work with a variety of igneous rock samples, using their observational skills to develop ways to categorize and identify the rocks. The suggested list of hand samples represents "common" igneous rocks that have a range of compositions and textures. To simplify the lab and/or reduce the time, one could curate the list to a smaller group of rocks (i.e. granite, diorite, gabbro, rhyolite, andesite, basalt). Larger, "mystery rock" samples should be selected to include the types of igneous compositions and textures students will learn to identify using the smaller hand samples. Hand lenses or magnifying glasses can be used for closer observations. Students can record observations and interpretations as a group on white boards, chalkboards, or large sheets of paper, or can each maintain their own notes on electronic or hard copy student packets. In addition, shared information can also be posted on a classroom white or chalkboard (e.g., igneous rock terminology and hand sample IDs) for everyone to see and discuss.

Igneous Rocks Inquiry Lab - Instructor Notes (Microsoft Word 2007 (.docx) 15kB Jul28 21)
Igneous Rocks Inquiry Lab - Student Packet (Microsoft Word 2007 (.docx) 114kB Jul28 21)
Igneous Rocks Inquiry Lab Slides (PowerPoint 2007 (.pptx) 26.3MB Jul28 21)

Teaching Notes and Tips

RiThis lab activity asks students to collaborate on learning about igneous rocks. As presented, instructors should act as a "guide on the side" for much of the activity, encouraging students to teach each other and share resources.

Some moments/points where students may need guidance:
Sketching Exercise - Remind students that artistic skill is not needed - this work is meant to document the rock. (The goal should be that someone else could use the sketch to pick the particular rock out of a group.) Also, sketches can include written notes, observations, interpretations and questions. Students should spend at least 10 minutes on this activity - encourage them to really spend the entire time observing their rock and adding detail and annotations to their sketches.
Group Teachout - instructors should help summarize and consolidate definitions and examples for each term to be sure all students understand the definitions and defining characteristics. (Instructors can add terms as needed for larger groups.)
Igneous Rock Identification Scheme - instructors should plan to walk through the graphic as a group, perhaps using one of the hand samples as an example for the whole class. (e.g., basalt - mafic or felsic? Look on the chart, and determine what identifications apply...)
Hand Sample Identification - Some igneous rocks (e.g., andesite) can be difficult to identify depending on the characteristics of the particular hand sample. Instructors should be ready to offer some support while reminding students that this is all natural material so some variation from an ideal specimen should be expected. This is a great opportunity to share with students that in the geosciences, the whole outdoors is our lab and that there are variations beyond what may be pictured in a textbook or on a web site.


There are a number of opportunities for formative assessment during this activity. Depending on the size of the group and the time allotted, instructors can circulate to discuss student work during each section of the student packet. Verifying that students have completed the Group Teachout with complete and accurate information, verifying correct identification of the provided hand samples, verifying the identification of the Mystery Rocks, asking students to "tell the story" of any given rock sample, and asking students to predict what kind(s) of igneous rocks they might find at different plate tectonic settings are all potential moments during the lab for assessment.

An additional summative assessment could be added during which students are given new samples for identification, asked to "tell the story" of an igneous rock, or given a plate tectonic setting and asked to predict what kind of igneous rock they would expect to find there. This could be in the form of an igneous rocks lab quiz, a more holistic "all rocks" quiz, and/or through questions on an exam.

References and Resources